A Quantum Leap

“As I have said so many times,
God doesn’t play dice with the world.”
Albert Einstein, 1942

Einstein’s quote comes from a conversation with author William Hermanns, in which Einstein expressed his dissatisfaction with the theories concerning the existence of quantum phenomena. Clearly, quantum mechanics isn’t the easiest concept to grasp. Nonetheless, in the past decade many researchers here at Harvard have endeavored not only to tackle the complexities of quantum mechanics, but also to apply these principles to computers. As a fairly new field, quantum computing is quickly maturing, and the possibilities, although difficult to envision, are endless.

But what exactly is a quantum computer? Essentially, it is a computer that uses the principles of quantum mechanics to work with data by facilitating memory storage and operations. One example is the use of electron
spin, which acts much like the on/off nature of a transistor in classical computers. With the use of atomic data storage and manipulation, quantum computers could evolutionize and perhaps replace all of our current computing technology. They would be far more efficient than classical computers and could store boundless amounts of memory.

Among many Harvard researchers actively involved in this research, Dr. Alan Aspuru-Guzik, a theoretical chemist and professor of Physical Sciences 1, and Dr. Marco Lončar, an engineer and recently-tenured professor, are both particularly enamored by the idea of a quantum computer.

As an undergraduate, Aspuru-Guzik did not study quantum computing, likely because the field was still growing and gaining recognition. When asked if he ever expected to be studying quantum computing, he responded, “There is this Latin American song that says the ways of life are not as I imagine them. This is what I tell everyone when they are starting out.”

It wasn’t until Aspuru-Guzik was a post-doctoral student that his adviser offered him grant money to research the intersection of computers and quantum phenomenon in chemistry. It was a direction that he had never considered before, but one that quickly became his central interest. Ultimately, his research as a postdoc led him to a very successful paper and eventually a job at Harvard.

“You start in a general direction and then life takes you in its own way, in very strange directions,” he said.

If it weren’t for the development of the field of quantum computing near the end of the 20th century, Aspuru-Guzik would likely have found himself with completely different research interests. The birth of quantum computing is a peculiar story. In the decades following the Second World War, many physicists found themselves out of work despite their education. Such was the case throughout the 1970’s at the University of California Berkeley where many ‘hippie’ physicists bided their time contemplating quantum mechanics. This story is depicted in detail in David Kaiser’s new book “How the Hippies Saved Physics.”

Soon, scientists too began to consider the applications of quantum mechanics, especially to computers. The field of quantum computing officially began when Richard Feynman published his 1982 paper entitled Simulating Physics with Computers. However, it wasn’t until Peter Shor created his quantum algorithm for factorization that research in the field of quantum computing began gaining more recognition and funding.

Today, Aspuru-Guzik studies the interface between quantum mechanics and the phenomena that happen in chemistry.

“This takes us from the most practical aspects from how solar cells capture energy to thinking about how, if you had a quantum computer large enough, you could simulate physical systems efficiently,” he explains. “Current computers are inefficient.”

On a day-to-day basis, it is the privilege of getting to see research happen in real time that pulls Aspuru-Guzik up in the morning. He also loves to teach and embraces new ways of teaching difficult concepts to his
freshman students. When asked when he thinks the first quantum computer will be available, Aspuru-Guzik said, “Some days I think that there will be a quantum computer in a few years, some days I think it will take 25 years or longer. It’s hard to tell, but I will tell you something: thinking about quantum mechanics has taught us many interesting things.”

While different in many aspects, Dr. Marco Lončar’s research also boils down to the atomic level. “What we are interested in when it comes to quantum computing is building a solid state platform,” he explains.“You would have a quantum processor much like the one that is in your computer today but could do the same job much more efficiently.”

The basis of this processor is a system of independently suspended atoms within the stringent lattice of a diamond. Essentially, you remove one carbon atom from the diamond lattice and replace it with nitrogen. You can do this many times with atoms of nitrogen.

“These nitrogen vacancy atoms have two important properties, one being electron spin that can be controlled,” Lončar said. “You can put it in one of the two spins as the basis of quantum memory. What’s nice about it is this spin can live for long periods of time, milliseconds to seconds. The second nice feature is you can read out the spin state using light. You can count how many photons come back. Billions of quantum nodes could replace transistors.”

While these two professors have very different approaches to understanding the interface between computing and quantum phenomenon, they both see much potential in the field. Similar to Aspuru-Guzik, Lončar finds it difficult to make any predictions regarding when the first quantum computer will emerge from all these collaborative efforts.

“This field has been around for quite a bit of time but the diamond is a new approach. People like me get into this field because it is a promising platform and is quite optimistic, but I would hate to make any predictions.”